I'm experiencing a slight hiss in my M3. It's very faint but I can always kind of hear it, even when I turn the radio off by pressing the volume button in. Im really unsure as to what it may be? but it's sort of starting to annoy me. Im 23 and recently had a hearing test and I daily the car so it's obvious to me, but the shop foreman at my local BMW was unable to hear it while I had my car in for service.. so I sort of let it go for then.

Is there anything I can try to weed out what it may be?

The best way I can describe it is like a aux cable being unplugged and while the volume is up, but slightly more faint of a hiss.

I was even thinking maybe updating all my software from the dealer would cure it?